1. Field of the Invention
The present invention relates to an electronic musical instrument which is ideal for use in the synthesis of acoustic musical instruments such as wind instruments or string instruments.
2. Prior Art
Electronic musical instruments have been conventionally known which electronically synthesize the musical tones generated by acoustic musical instruments such as wind instruments or string instruments. This type of electronic musical instrument has some sort of tone source for the synthesis of musical tones. In this tone source, an apparatus is known in which a memory is used in which waveform signals which form the bases of musical tones are stored in advance, and at the time of tone generation, various types of processing are conducted on a waveform signal which is read out from the memory and a musical tone is generated, and an apparatus is known in which the musical tones of an acoustic musical instrument are synthesized by means of the simulation of the tone generation mechanism of an acoustic musical instrument by means of an electronic circuit.
In particular, the tone source which simulates a tone generation mechanism, which will be discussed hereinafter, has a closed loop circuit comprising delay circuits, filters, non-linear circuits and the like. By means of this tone source, a musical tone which is somewhat close to the tone of an acoustic musical instrument can be synthesized by means of the adjustment of musical tone synthesis parameters, for example the delay length of delay circuits. This type of technology is disclosed in, for example, Japanese Patent Application, First Publication, Laid open number Sho. 63-40199, and in Japanese Patent Application, Second Publication number Sho. 58-58679.
In the above described conventional electronic musical instruments, the pitch of the musical tone is determined by the total amount of the delay of the delay circuits. However, in actuality, as a result of other parameters such as filter characteristics and the like, the transmission speed is as high as that of a high frequency signal, for example, and so the transmission speed varies in accordance with the pitch of the tone which is to be synthesized. Accordingly, when the delay length of the delay circuit is set univocally, there is a problem in that the musical tone having a desired pitch can not be achieved.
Furthermore, in conventional electronic musical instruments, when a performer manipulates the various parameters (delay length of the delay circuit or filter characteristics or the like ) of the musical tone synthesis circuit in order to set the tone color and the like of the musical tones, fluctuations are generated in the pitch of the musical tones for the above given reasons. Accordingly, there has been a problem in that in the case of the performance of a performer who is unable to conduct accurate pitch control, or in the case of the use of a keyboard musical instrument or the like having controls which can not control pitch, the pitch is inaccurate.